CA1330936C

CA1330936C - Hydrophilic polymers for incorporating deodorants into absorbent structures

Info

Publication number: CA1330936C
Application number: CA000575833A
Authority: CA
Inventors: Shmuel Dabi
Original assignee: Personal Products Co
Current assignee: Personal Products Co
Priority date: 1987-08-28
Filing date: 1988-08-26
Publication date: 1994-07-26
Anticipated expiration: 2011-07-26
Also published as: PH26761A; IE61194B1; JPS6483264A; DE3877281D1; ATE84225T1; DE3877281T2; US4992326A; IE882613L; GR880100555A; EP0304952A2; ES2053649T3; EP0304952B1; IN171312B; ZA886375B; NZ225846A; CN1031545A; JP2868522B2; AU2143088A; GR1000338B; EP0304952A3

Abstract

HYDROPHILIC POLYMERS FOR INCORPORATING
DEODORANTS IN ABSORBENT STRUCTURES

Abstract There is disclosed the process of incorporating a deodorant powder (of various mechanisms of action) into a hydrophilic, swellable, water-insoluble absorbent crosslinked polymer, which swellable polymer is coated on a thin, flexible, substrate e.g.
a non-woven web, a paper tissue, or a water-insensitive film, and the resultant flexible structures which contain the deodorant powders, held in a dust-free stable manner, and their use as one or more components of body fluid absorbent structures such as sanitary napkins.

Description

~" ~33~6 HYDROPHILIC POLYMERS FOR INCORPORATING ~.
DEODORANTS IN A~SORBENT STRUCTURES

This invention relates to the process of incorporating a deodorant powder into a hydrophil;c, swellable, water-insoluble absorbent crosslinked polymer, which swellable polymer is coated on a thin, fle~ible, substrate e.g. a non-woven web, a paper tissue, or a water-insensitive film, and to the resultant flesible structures which contain the deodorant powders, held in a dust-free stable manner, and their use as components of body fluid absorbent structures.

Backqround of the Invention The odor associated with body discharges, such as menstrual fluid and urine, can be effectively eliminated or reduced by many active compounds. The reduction in odor can be accomplished throllgh various mechanisms: 1) by the active ingredient attacking and killing the organism which forms the odorous materials te.g.,bactericide); 2~ by it -~
interfering with the metabolism cycle which leads to the -formation of odor (anti-enzyme, e.g., EDTA); 3) by chemical neutralization of the odorous materials (e.g., ~;
sodium bicarbonate neutralizes fatty acids); 4) by strong physical adsorption of materials (e.g., activated charcoal). Other mechanisms are also known. The terms ~deodorant~ and ~antiodorant~ as used herein interchangeably, are intended to include all such active ingredients, no matter what specific deodorizing mechanism is involved.

Most antiodorant materials are available only in powder ;;
form, and as such, are dusty and difficult to incorporate and contain in commercial body fluid absorbent products . .
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133~936 such as sanitary napkins or diapers. Additionally, good (and sometimes long) contact must be established between the active deodorant compounds and the body fluid, before ~ -odor reduction can be realized.
The present invention serves to solve some of these problems by means of a polymeric system which facilitates the incorporation of antiodorant powders into sanitary napkins and other absorbent products and contains them in a dust free manner, while allowing a good contact with the absorbed body fluid. The term ~sanitary napkin" as used herein is intended to include all products conventionally used to absorb menstrual fluid or vaginal discharge, which are not tampons, whether referred to as sanitary napkins, panty shields, panty liners or similar or synonymous names.
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Prior Art Kimberly-Clark U.S. patent 4,547,195 describes a sanitary napkin having a malodor counteracting agent added to a batt of absorbent material which is then folded so the antiodorant agent is concentrated near the most absorbent site. Another means to achieve greater utilization of the -active ingredient is disclosed in 8eghin-Say's WO
8403-631-A, where a justaposition of superabsorbent particles and antibacterial agent is claimed. The composition is made by slurring an insoluble polyelectrolyte (superabsorbent) and antibacterial agent in methanol followed by evaporation. This creates some adhesion between the two substances. However, powders,in general, would not be contained to form a dust-free product, since they are not embedded in the polymer.

The advantage of the present invention over the prior art is that it allows the formation of a dust-free structure ~i , lPPC 295 .~

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by anchoring the active deodorant powde~, yet the active ingredient is still efficacious. Another important advantage of the above proc~ss is that the powder/water swellable composite can be /formed in si~u on any substrate, which can then be u)sed in any desired specific location in the final product.

SummarY of the Inven~

10 The present in~ention is directed to a deodorant -powder-containing body ~luid absorbent structure comprising a thin, fle~ible substrate such as a non-woven web or a paper tissue or a water-insensitive film~ which -~
substrate is coated with a hydrophilic, wat8r insoluble, 15 -water swellable crosslinked polymeric film containing a ~-powdered deodorant immobilized in a dust-free manner by being completely or partially incorporated in said polymeric film coating, and to the components thereof i.e.
the coated substrate having the powdered deodora~t 20 immobilized in the swellable crosslinked polym ~lc film ~-coating.
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~ Detailed De$çription of the Invention . .
; 25 The polymeric system of this invention utilizes hydrophilic, water swellable, water insoluble absorbent polymers (i.e. absorbents and superabsorbents) which ;~
completely or partially encapsulate the active deodorant powder. The prefered polymers are water soluble, film forming polymers, which are rendered insoluble by crosslinking them. Esamples of such polymers include ammonium or alkali metal salts of poly(meth) acrylic acid, polyacrylamide, poly vinyl alcohol, and starch derivatives. These and other usable polymers are described in U.S. Patents 3,926,891 (Dow), 4,154,~98 (Dow~

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_4_ and 4,645,7B5 (Personal Products), and in the book ~Water Soluble Resins~ by R. L. Davidson, Reinhold Publishing Corp., 1962. p. 106, and are well known materials.

Prior to the insolubilization (or crosslinking) step, the active antiodorant powder is dispersed in the polymer solution which is then crosslinked and dried. In many cases the powder-containing polymer solution can be applied onto substrates such as a non-woven web of te~tile fibers (typically made with polyester fibers) or paper tissue or water-insensitive film e.g. polypropylene and polyethylene film, and then crosslinked in ~i~ to form a thin coating on the substrate of water swellable polymer which contains acti~e antiodorant materials. The uniqueness of this composite is that the dusty deodorant powder is now well contained in a dust-free manner yet is available to perform its deodorizing function upon contact with aqueous fluids e.g. body discharges, which swell the ~; -encapsulating polymer. Moreover, the body discharge or other aqueous fluid is immobilized by the absorbent around the active deodorant and is held in intimate contact with the deodorant, thereby ma~imizing the efficacy of the deodorant.

The choice of the specific hydrophilic polymer to be used is dependent upon the type of active deodorant involved, the desired absorbent composite and the process conditions to be used for making the absorbent structure.

Most preferably, the process used will involve dispersing the active deodorant powder (or deodorant liquid where the deodorant is first dissolved in a solvent) in a water solution of the hydrophilic polymer, adding a crosslinker and then drying and crosslinking (see E~ample ~).

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Another prefered process is to first apply a film of the hydrophilic polymer and then spray it with a solution of a crosslinker or a gelling agent crosslinker (see Esample II). In this process the active deodorant could be 5 included in either component. The consecutive appli~ation ;
of polymer and gelling agent also helps to overcome many compatibility problems between the polymer solution and active ingredient. For esample, a water solution of polysodium acrylate would not tolerate even small amounts of active ingredients containing di or tri valent ions, such as calcium, magnesium and aluminum. In this case, layers of polymer and deodorant solution would be applied -~
in a consecutive manner.
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Since in the present invention the deodorant is fi~ed onto the substrate, it is now possible to design even more ~-effective deodorizing absorbent sanitary napkins and other such end product structures. Various deodorants are individually effective against certain causes of odors, but cannot be used together because they would react with each other if they were part of the same substrate coating. However, by separately incorporating such incompatible deodorants onto different substrates, and then using the different deodorant containing thin flesible substrates in layers in the final end product structure, the incompatibility problem can be solved. (see E~ample III, which shows how this can be done).
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The ratio of polymer to active ingredient is determined by ~ -`~ f 30 the final performance criteria and by the process ~
conditions. The ratios by weight percent range between 5% ~`
f powder ` ~5% polymer and B0% powder - 20% polymer for purposes of the present invention. ~ ;

Body fluid absorbent structures are usually composed of ".
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layers of materials, e.g. ~nany sanitary napkins and disposable diapers have a facing layer, a backing layer and an inside absorbent layer. The deodorant-containing water-swellable polymeric film coated thin-flesible S substrate made from non-woven web, paper tissue or water-insensitive film, of the present invention can easily be incorporated in any desired location in the body fluid absorbent structure. For esample, where a suitable non-woven web or impervious film already is being used as 10 part of the total sanitary napkin structure, it first can -~
be coated with a hydrophilic water insoluble water-swellable crosslinked polymeric film containing the ~ -desired powdered deodorant immobilized in said coating, and then used as before in the sanitary napkin 15- construction. While the actual placement of the coated substrate in the absorbent product structure is not critical to the instant invention, and it can be placed wherever it is wished to have the powdered deodorant -available to contact the body fluid as it is absorbed in 20 actual use, preferably it will be placed as close to the -body as possible e.g. on the body facing material, or immediately under the body facing layer.

Many commercially available types of sanitary napkins are -constructed somewhat similarly to that depicted in U.S.
Patent No. 4,217,901, which has a (1) rectangular absorbent pad (made of any suitable absorbent material e.g. comminuted wood pulp fibers, cotton linters, rayon fiber, cotton staple etc.) as the core, (2) a body fluid impervious barrier (made of polyethylene or polypropylene film) on the undergarment facing side of the absorbent pad, which is provi-ded to preclude absorbed body fluid from striking through and wetting or staining the undergarment. (3) A sheet of tissue paper surrounding the -~
absorbent pad, (4) a body fluid pervious cover (made of :::

~:33~3~j any of the commonly used absorbent product covers such as ;
gauze, non-woven material reinforced with adhesi~e binders etc.) enveloping the tissue paper wrapped absorbent pad and body fluid impervious cover, and (5) an optional adhesive strip on the undergarment facing surface for those products designed to be adhesively attached to the wearers undergarment.

The deodorant-containing substrate of the present invention e.g. the composite made according to Esample II, can be used as a layer directly under the facing material in the above types of sanitary napkin construction.

There are many other constructions known for sanitary napkins, panty liners, etc., some omitting the tissue paper (3) above, but most constructions do have an impervious layer (2) and an absorbent pad (1). ~;

The substrates of the present invention can be used in various places in the sanitary napkin, the choice of which would dictate the specific substrate desired, and they can even replace some of the required layers. Thus the water-insensitive film substrate could be used as the impervious layer (2) above, while the tissue paper substrate could replace that of (3) above, or could be used as a separate layer underneath the tissue paper (3), while the non-woven fiber substrate could be underneath the body fluid pervious cover of, (4) above, or be placed on either side of, or even in the inside of, the absorbent 30 pad (1) above. - -~

The subs~rates useful in the present invention can be made of any materials which can form a thin, flesible web or film. For use in commercial body fluid absorbent structures e.g., sanitary napkins and diapers where cost PPC 295 ~

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of raw materials and manufacturing is a serious consideration, esamples of suitablP substrates would include such non-woven webs as polyester and polypropylene webs, such paper tissue as crepe paper tissue commercially S available from Showano Paper Mills, Shawano Falls, ;~
Wisconsin, and such impervious films polyethylene and polypropylene films.

The following e~amples will better illustrate the ~;
invention, but are not intended to limit the invention.

E~amPle _l `' A loOg/aqueous solution of polyacrylic acid (12.5% solid, Acrysol A-5 from Rohm & Haas) was neutralized to pH = 7 with 6 9 of 50% sodium hydroside. Into that neutralized solution, 29 of activated charcoal (Darco G-60 from ICI) were slurried and 0.29 of a crosslinker (XAMA-7, Virginia Chemical-Celanese) was added. From the resultant solution, a 10-mil thick film was cast on a polyethylene sheet and dried for 20 minutes at 60C.

When the cast film coating was wetted with 1% NaCl a~ueous solution (simulating a body fluid), it swelled immediately, and the fluid was immobilized around the activated charcoal deodorant.

The specific polymer used in this esample can be successfully replaced by polymethacrylate salts and by any 30 other copolymer of (meth) acrylic acid which is water -soluble, at least in its salt form.

The specific deodorant, activated charcoal, uæed in this esample can be successfully replaced by other powdered deodorants.
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. ., g The specific substrate, polyethylene sheet, used in this example can be successfully replaced by other substrates -~
normally used to construct a sanitary napkin e.g. ~ -non-woven fibers, absorbent pads, tissue paper, which can then be used in the same way to construct a sanitary napkin containing one or more deodorants.

E~am~le 2 :
A 15% solution of poly ~vinyl alcohol) in water (8B%
hydrolized, 125,000 MW) was preared. Into 100 9 of that solution, 2.5 9 of sodium bicarbonate were dissolved. 6 9 of the resultant solution was cast into a 10-mil thick film on a silicon-coated release paper. The cast wet film was sprayed with 1.5 9 of a 2% aqueous solution of Borax (gelling cross-linker agent). The resultant wet gel was dried to leave a clear film in which sodium bicarbonate was encapsulated. Alternatively, the PVA/bicarbonate solution was coated on a thin polyester web (0.7 oz/sq.
yard) and sprayed with bora~ solution. The weight of the coating was about equal to the weight o the starting web. The coating was applied two different ways so that ;
in one case both sides of the web were coated, and in the other way only one side of the web was coated. This would be placed under the cover o~ a typical sanitary napkin where the web is coated on one side only, we prefer that the coated sides be away from the body. ~

A synthetic fluid consisting of isovaleric, butyric and --lactic acids in water (simulates a typical rancid odor) was deposited on the aforesaid film. The odor disappeared almost ihstantaneously. `~

Another esperiment was al~o conducted to demonstrate the . ,~ .- .

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availability of the encapsulated sodium bicarbonate: A S~
solution of lactic acid containing bromophenol blue indicator has a dark red color in pH lower than 5.
However, this solution turned blue, immediately after contacting the aforesaid film with it, indicating effective neutralization of the lactic acid by the encapsulated sodium carbonate.

E~amPle 3 ' ~' In this e~ample two incompatible deodorants are separately fi~ed onto two different substrates, so more effective structures can be designed. One such structure would `
separate an acid neutralizing material ~sodium bicarbonate) from an amine neutralizing material ~poly acrylic acid), so that each one would be active against the corresponding odorant, but they would not neutralize each other. Thus, a first layer is prepared by coating the poly vinyl alcohol and sodium bicarbonate solution described in Example I, on a 0.7 oz.~sq. yd. polyester web. The total add-on ratio of powder and PVA to the web is 1:1. A second layer is prepared by coating a 0.7 oz./sq. yd. polyester web with the polyacrylic acid/charcoal composition described in Esample I, escept 25 that the polyacrylic acid was neutralized to pH = 4. The ;~
add-on ratio is again 1:1. By leaving most of the carbo~ylic groups in their acid form, this layer can ;
neutralize immediately ammonia and amine type odors, which are not affected by the top layer. The two layers can be incorporated into a sanitary napkin as a unitized deodorant insert as des~ribed above. -;
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Claims

1. A method of making a flexible structure suitable for use as a component of a body fluid absorbent structure, comprising: a thin, flexible substrate in the form of a non-woven web, or a paper tissue or a water-insensitive film, which substrate is coated with a hydrophilic, water insoluble, water swellable polymeric film containing a powdered deodorant immobilized in a dust-free manner in said polymeric film, by the steps comprising: applying a dispersion of the powdered deodorant in an aqueous solution of a water-soluble film forming polymer onto the substrate and then cross-linking the polymer in situ to form the water swellable polymeric film on said substrate, the ratio of polymer to powdered deodorant ranging between 5%
powdered deodorant - 95% polymer and 80% powdered deodorant - 20% polymer.

2. A powdered deodorant immobilized in a dust-free manner by being completely or partially encapsulated in a hydrophilic, water-insoluble, water-swellable cross-linked polymeric film, wherein the ratio of polymeric film to powdered deodorant ranges between 5% powdered deodorant - 95% polymeric film and 80% powdered deodorant - 20% polymeric film.

3. A thin, flexible substrate in the form of a non-woven web, a paper tissue or a water insensitive film, coated with a hydrophilic, water-insoluble, water-swellable cross-linked polymeric film containing a powdered deodorant immobilized in a dust-free manner by being completely or partially encapsulated in said polymeric film, wherein the ratio of polymeric film to powdered deodorant ranges between 5% powdered deodorant - 95% polymeric film and 80% powdered deodorant - 20% polymeric film.

4. A sanitary napkin containing, as part of its construction, the substrate according to claim 3.

5. A sanitary napkin according to claim 4, wherein the deodorant-containing substrate is placed directly under the body facing material layer of the napkin.

6. A sanitary napkin according to claim 4, wherein the body facing material layer of the napkin has been treated with polyvinyl alcohol-bicarbonate-borax.

7. The sanitary napkin of claim 6 where only the inner surface of the body facing layer has been treated with polyvinyl alcohol-bicarbonate-borax.

8. A sanitary napkin containing as part of its construction, at least two different substrates according to claim 3, each of said substrates having a different powdered deodorant coated thereon.

9. A sanitary napkin according to claim 8 wherein said different powdered deodorants used are of the types which would be incompatible if used together as part of the same substrate coating.